Invasive Mink Threatens South America's Largest Woodpecker

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Invasive American minks may threaten the largest woodpecker
species in South America, according to new research.

The Magellanic woodpecker — a relative of the
extinct ivory-billed woodpecker — lives throughout the Andes
of Chile and Argentina. The large birds only produce one
offspring per year and maintain broad territorial boundaries of
about 1 square kilometer (0.4 square miles) per male-female pair,
limiting the density and growth of their population.

Still, the charismatic
birds maintain stable populations by holing up in branchless,
dead trees that carnivores struggle to climb. Until now, there
have been no records of predation on the birds.

But researchers based at the University of North Texas in Denton
and the University of Santiago in Chile report they have now
found the first evidence of Magellanic predation on Navarino
Island — a 955-square-mile (2,473 square kilometers) island off
the coast of Southern Chile — by the American mink, a carnivore
native to northern North America that was introduced to South
America in the 1930s for fur farming. Minks that escaped these
farms have since multiplied and
have become an invasive species, without any natural
predators in the region. [ In
Photos: The Peskiest Alien Mammals ]

Though the team did not make direct observations of a
mink attacking a woodpecker, they collected several pieces of
evidence to argue their case, which they detailed earlier this
month in the journal Biological Invasions.

For instance, the team found an adult Magellanic woodpecker —
which they had outfitted with a radio-tag for an unrelated study
— dead within a mink den. While it's possible a mink had found
the bird already dead and scavenged it in the den, this type of
behavior would be atypical of carnivores that tend to hunt live
prey, said Jaime Jimenez, a researcher at the University of North
Texas and a co-author on the paper.

On a separate occasion, the team observed a mink creep up on a
woodpecker, looking ready to pounce at about 1 foot away (30
centimeters) until a student scared it off to prevent the attack.

And, finally, the team stationed cameras around the island,
revealing footage of minks and woodpeckers feeding in the same
areas of the forest floor — on separate occasions, but sometimes
within minutes of each other — suggesting the animals share the
same habitat. This would make the woodpeckers vulnerable to
predation, if the minks had this intent.

The team thinks the woodpeckers have adapted to feed on the
forest floor, rather than holing up more cautiously in trees,
because they historically have had no natural predators on the
island.

"They may have become naïve by not having been exposed to
terrestrial carnivores," Jimenez told LiveScience. "It's very
easy for a carnivore to pounce on a woodpecker and kill it."

The team believes this predation could result in a significant
decline in the bird population on the island, which could result
in other indirect ecological consequences, including a spike in
insect populations that the birds would otherwise feed on. Other
birds, including owls and parakeets, also use the Magellanic's
vacated holes as breeding grounds, and may lose this important
habitat if the woodpecker populations decline, Jimenez told
LiveScience.

The team next plans to attach GPS units to the woodpeckers to
better assess their distribution across the island and understand
the ecological consequences of their potential decline, in an
effort to develop management plans in response to the invasive
mink population.

Editor's note:This article has
been updated to correct Jaime Jimenez's affiliation. He is a
researcher at the University of North Texas, not the University
of Texas.